Historically, a curling hack consisted of a notch or depression carved in a sheet of ice. A curler would stand with one foot in the hack while throwing a curling rock. The hack provided the curler with stable footing when throwing the curling rock.
In modern curling the curler no longer stands when throwing the curling rock. Instead the curler slides part way down the sheet of ice with the curling rock. The curling hack is still important as it provides a point against which the curler can push to commence the slide.
Despite its importance to the game of curling, the conventional curling hack consisting of a notch or depression in the ice surface presents a number of problems. The persons who care for and maintain the ice surface must continually remove accumulations of broom straw and debris from the hacks. When "pebbling" the ice, they must take care not to allow ice to accumulate within the hack for fear that a curler may slip and fall while attempting to push out of the hack to commence his or her slide. During the playing of the game, the curlers must prevent curling rocks from falling into and potentially damaging the hacks. It is not unusual for a curler, while absorbed in watching the curling action, to inadvertently step down into the notch or depression forming the hack and fall or otherwise injure himself or herself.
In order to make caring for the ice easier above ice surface curling hacks have been developed that rest on top of the ice surface. These curling hacks consist of an arm having a first end pivotally mounted at an end of a sheet of curling ice and a second end having a foot pad. When the curlers wish to throw curling rocks, the arm is laid down parallel to the ice surface with the foot pad resting on the ice surface where a conventional hack would normally be. When the ice is being serviced, or when not required during a curling game, the arm is pivoted into a position raised from the ice surface. To accommodate both curlers who push off on their right foot and curlers who push off on their left foot, the arm is laterally slidable.
The concept of an above ice surface curling hack provided tremendous advantages and convenience for the persons servicing the ice. Numerous complaints, however, were received from the curlers. The mechanism that allowed the arm to move laterally, unavoidably developed some unwanted movement after prolonged use that adversely effected the curlers push off. In the raised position, the arm itself became a hazard which was often inadvertently bumped by curlers. For these and other reasons, the above ice surface curling hacks did not become popular with curlers.